The generative approach to SLA and its place in modern ...

The generative approach to SLA and its place in modern second language studies Article

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Rothman, J. and Slabakova, R. (2018) The generative approach to SLA and its place in modern second language studies. Studies in Second Language Acquisition, 40 (2). pp. 417-442. ISSN 1470-1545 doi: https://doi.org/10.1017/S0272263117000134 Available at https://centaur.reading.ac.uk/69574/

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The State of the Science in Generative SLA and Its Place in Modern Second Language

Studies

Jason Rothman

University of Reading and UiT The Arctic University of Norway

Roumyana Slabakova

University of Southampton and University of Iowa

Address for correspondence:

Roumyana Slabakova

Modern Languages

The University of Southampton

Avenue Campus 65/3029

Southampton

SO17 1BF

UK

[email protected]

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ABSTRACT

This article has two main goals. The first is to summarize and comment on the current state-of-

affairs of generative approaches to SLA (GenSLA), thirty-five years into its history. This

discussion brings the readership of SSLA up-to-date on the questions driving GenSLA agendas

and clears up misconceptions about what GenSLA does and does not endeavor to explain. We

engage key questions/debates/shifts within GenSLA such as focusing on the deterministic role of

input in language acquisition, as well as expanding the inquiry to new populations and empirical

methodologies and technologies used. The second goal is to highlight the place of GenSLA in

the broader field of SLA. We argue that various theories of SLA are needed, showing that many

existing SLA paradigms are much less mutually exclusive than commonly believed (cf. Rothman

& VanPatten, 2013; Slabakova et al., 2014, 2015; VanPatten & Rothman, 2014) — especially in

light of their different foci and research questions.

Introduction

In the broadest sense, Second Language Acquisition (SLA) studies endeavor to describe

and explain how non-native languages are acquired, processed and used. Inherent to the process

of SLA are transitional stages—interlanguage development—along a complex developmental

continuum. The number of variables that affect SLA are undoubtedly many, ranging from

linguistic and cognitive to individual and societal. The explanatory power of SLA theories

crucially depends on uncovering which particular variables are more or less influential at specific

points of development and what their degree of influence is along the developmental continuum.

Because there are so many aspects/variables to SLA that can be the specific focus of particular

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theories, it is not surprising that there are so many approaches to SLA. Each adds to the general

field by isolating, describing and explaining specific factors that influence linguistic performance

and competence in adult non-native language learners.

Given the comparative youth of SLA research, it is even less surprising that paradigmatic

misconceptions abound, fueling perceptions of incompatibility or mutual exclusivity among

various SLA approaches. To be sure, there are views across paradigms that are truly mutually

exclusive; that is, either one or the other (and likely neither) is correct in absolute terms, but both

cannot be because of their dichotomous nature. This is also true of competing theories within a

paradigm. Specific theories within generative approaches to SLA (GenSLA) can be mutually

exclusive (see Slabakova, 2016; White, 2003). For example, models that claim full transfer at the

initial stages of adult SLA, such as Full Transfer/Full Access (Schwartz & Sprouse, 1996), are

mutually exclusive to theories maintaining very limited or no transfer of functional

categories/features such as Minimal Trees (Vainikka & Young Scholten, 1994, 1996). However,

the actual level of incompatibility across paradigms, in our view, is much less than what is

largely held true (Rothman & VanPatten, 2013; Slabakova, Leal Mendez & Liskin-Gasparro,

2015; but see de Bot, 2015, for arguments against) in large part because the questions each

paradigm pursues are only partially overlapping. In addition to valid and appropriate scientific

debates on the perception of significant incompatibility across various SLA paradigms, there are

historical reasons for blatant misunderstanding of what particular SLA theories actually claim.

Unfortunately, an inevitable consequence of this fact is that young scholars are sometimes

trained without being afforded the opportunity to understand for themselves why approach X is

supposedly so ill-conceived, and, by extension, why approach Y is superior in certain respects.

Another unintentional byproduct is that the newest generation of scholars is perhaps less

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prepared than its predecessor to fully appreciate the role of competing paradigms in the broader

field of SLA. Scientific progress runs the risk of being thwarted when one allows for

misconceptions regarding false dichotomies to continue unabated. The ultimate goal of SLA is

shared across all scholars: to be increasingly more accurate in our descriptions and explanations.

The history of scientific inquiry itself, regardless of the discipline, has shown that virtually no

theory at any snapshot in time is completely correct. This is unproblematic since the goal of

science is not to be “right”, but rather increasingly more accurate over time. In all likelihood, no

current theory of SLA is “correct” in absolute terms, but understanding competing theories

accurately is the only way to perform the remit of science: a theory can only be meaningfully

excluded from further consideration to the extent that it is properly understood.

The intended audiences of this article are graduate students and young scholars in the

extended field of SLA. It has several interrelated goals. First, we offer a state-of-the-science of

GenSLA, orienting the readers to the main questions and trends in today’s GenSLA as opposed

to questions of primary focus from 30 years ago. Second, we highlight where mutual exclusivity

exists between GenSLA and usage-based approaches to SLA (e.g., Ellis & Larsen Freeman

2009a,b; Ellis & Wulff, 2015; Wulff & Ellis, to appear) and where we believe claims of

incompatibility reflect misunderstanding more than anything tangible. Finally, we offer some

insights into where we feel GenSLA is likely to progress in the near future and how this fits

within the broader field of SLA studies.

The Main Tenets of GenSLA

Like other cognitive based theories of SLA, GenSLA has always focused on describing

and explaining the system of implicit second language (L2) knowledge, especially how it comes

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to be represented in the mind/brain of the learner. The aim of much research in GenSLA from its

beginning in the 1980s has been to provide an understanding of the interplay between knowledge

pertaining to all human languages (henceforth Universal Grammar or UG), knowledge that

comes from the mother tongue (henceforth L1 transfer), and knowledge that comes from

exposure to the target language (henceforth acquisition based on L2 input). In an effort to

contextualize the past of GenSLA studies, we provide a cursory summary of the two main

questions that drove the research programs in GenSLA for the first two decades. Clearly, we

cannot do justice to everything worthy of discussion from the early years of GenSLA. We

sacrifice nuanced details in an effort to carve out space to dedicate ourselves to present-day

GenSLA and also because there are high quality and detailed summaries of the early years in

existence to which we refer the reader (e.g., White 1989, 2003).

Akin to other mental systems that need external stimuli to unfold (e.g., vision), UG is

argued to be a genetically endowed blueprint to the most generalizable facts about language; that

is, it contains the linguistic information that is common to all human languages, labeled

principles. As concerns linguistic learnability, the idea is that UG fills the gap left by what is

learnable based on input and domain general cognition alone. Equipped with UG, child learners

are able to narrow down the search space for language learning by limiting their hypotheses

about the target language from the superset of all logical possibilities to the subset UG allows;

that is, only those that characterize potential human grammars. In listing a priori the limits on

what is and what is not a possible grammar, UG also identifies and restricts the parameters of

grammatical variation between languages. Clearly, many domain-general cognitive, social, and

computational principles shape linguistic development. According to the generative perspective,

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all these factors in consort are the arsenal learners bring to the task of organizing and making

sense of the input they encounter.

From its inception, generative language acquisition has been powered by the logical

problem of language acquisition; namely, it defies logic that children should acquire their native

language so fast and with so little trial and error, if the input that they are exposed to is uneven,

inconsistent and frequently under-represents the knowledge they ultimately acquire. The

argument is that acquisition processes are streamlined by domain-specific linguistic knowledge

with which children are hypothesized to be born (e.g., Fodor, 1983; Pinker, 1995). Support for

domain-specific linguistic knowledge comes from the Poverty of the Stimulus (PoS) argument

(e.g., Schwartz & Sprouse 2000, 2013; see an extended example below). The logic goes like this:

If one can show that a child’s knowledge of grammar extends beyond what could possibly be

deduced from the input, even allowing for the operation of general cognitive principles,

processing and learning mechanisms, then such knowledge is left unaccounted for. If such

unaccounted-for knowledge is arrived at by all learners despite the same improbability of

extracting such knowledge from input or the gap being filled by domain-general cognitive

mechanisms, then this constitutes good evidence that such a learner must have access to some

built-in knowledge regarding what shape natural grammars can take.

From its outset, GenSLA was also powered by the logical problem of language

acquisition and by discussions of how it applies to the learning of second and subsequent

languages in adulthood (White, 1989; Schwartz 1998). Linguists who accept that UG continues

to be accessible in adulthood and thus constrains L2 acquisition point to knowledge that is

demonstrably present in L2 interlanguage grammars, but could not be acquired based on

observation of the input alone, transferred from the native language, or taught explicitly in the

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case of classroom learners. The learnability issues highlighted by the PoS argument extend

beyond evidence-based but constrained acquisition to knowledge of what is unacceptable despite

a bankruptcy of input cues that should lead the learner to deduce this.

The most important research question that dominated the field during the 1980s and at

least the beginning of the 1990s was: Is there or is there not access to UG in adult SLA? The

dichotomous nature of this research question echoed the Critical Period (CP) Hypothesis debates

at the time: is SLA subject to a critical period or not? In other words, the generative linguistic

equivalent to the critical period was essentially maturationally conditioned accessibility to UG.

Gray areas or degrees of success in L2 acquisition were not easily accommodated by the theory.

In Bley-Vroman’s formulation (Bley-Vroman, 1989, 1990; see Bley-Vroman, 2009 for an

update), SLA was a fundamentally different process from native language acquisition because

L2 learners did not have direct access to UG after the critical period.

Empirical evidence from the 1970s and 1980s convincingly pointed in the direction of a

critical period for child first language acquisition; that is, a reduced ability over time to acquire

the functional L1 morphosyntactic system (e.g., Curtiss, 1977, 1988). Extending the notion of a

critical period to apply to the acquisition of all new morphosyntax after puberty seemed logical,

especially because the path and outcomes of adult L2 acquisition, partially like the case of very

late acquired L1 acquisition (e.g., Genie and other ‘wild children’), also differ from child

acquisition. However, it is certainly not the case that typical adult L2 acquisition presents

similarly to very late first language acquisition in adulthood (e.g. Mayberry, 1994). It could be

the case that a critical period (or lack of UG accessibility) pertains to all adults or that adult L2

learners are seemingly more successful than very late adult L1 learners because only the former

can build off of a previously acquired language. Alternatively, it might be the case that a critical

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period relates only to activating domain-specific information. In other words, having engaged

UG in childhood, typical adult L2 learners continue to have access to UG in adulthood whereas

the very late adult L1 learners did not activate UG prior to the critical period.

While it was assumed that UG was operable in child first language acquisition,

constraining acquisition options and leading the child on a relatively error-free developmental

path, determining whether adults had continued access to UG was not at all trivial; it was hotly

debated. The answer revolved around establishing evidence of grammatical knowledge that went

beyond what the language learners encountered, both in and outside classroom instruction.

Starting in the 1990s, a line of research in GenSLA concentrated on testing whether or not L2

learners did indeed acquire properties of the L2 incidentally, and specifically, do L2 learners

acquire PoS properties. Early work such as that by Kanno (1997), Perez-Leroux and Glass

(1999), Dekydtspotter, Sprouse and Anderson (1997) and Dekydtspotter, Sprouse and Thyre

(2000), among many others since, have showed that L2 grammars, despite significant differences

from L1 grammars, instantiate universal linguistic properties that cannot be linked to transfer or

accounted for by learning in the truest sense of the word (for an extended example, see the next

section). Such evidence seriously questions any claims for a fundamental difference between L1

and L2 acquisition. Although it is still not agreed by all within GenSLA that adults have direct

access to UG, PoS knowledge in adult L2 acquisition constitutes rather strong evidence that

adults continue to access UG past puberty. Differences between adults and children are explained

on the basis of something other than UG-accessibility.

At the same time, another factor played into that central question, partitioning the

possible answers. Since the native language of any learner contains the information universally

present in all of human language (i.e., the linguistic principles), clearly this information was

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available for transfer into the L2. Linguistic properties were divided into three types: universal

properties; parameterized properties whose values were transferable from the native language;

and values that were not transferable. Clearly, the parametric options depend on the L1–L2

pairings. For example, learning Italian null subjects would be easier if your native language is

Spanish, unlike if it were English. The interplay of UG access and L1 transfer allowed for a

number of positions: UG is fully accessible (e.g., White, 1989; Epstein, Flynn & Martohardjono,

1996; Schwartz & Sprouse, 1996; Vainikka & Young Scholten, 1994); UG is accessible through

the L1 only (Bley-Vroman, 1991); and UG constrains only L1 acquisition and is inaccessible in

SLA (Clahsen & Muysken, 1986; Meisel, 1997). In addition, as presciently argued by Hale

(1996), it may be exceedingly difficult to differentiate whether it is access to Minimalist UG or

L1 transfer that guides L2A.

In summary, despite the observable fact that in some ways adult L2 acquisition is

different from child L1 acquisition in path and ultimate attainment, the first two decades of

GenSLA research provided robust evidence that L2 interlanguage grammars instantiate abstract

knowledge about the L2 that could not have been acquired on the basis of the L2 input, transfer

from the L1 and/or instruction alone. Access to UG and the nature of L1 transfer were couched

within this learnability context.

Towards the Here and Now

The late 1990s and the 2000s saw some significant theoretical developments in GenSLA,

mostly inspired by changes in generative linguistic theory, namely, the Minimalist Program

(Chomsky, 1995). Although the idea of the feature as a unit of analysis at the right level of

granularity (abstraction) was always present in the formulation of parameters, it now came fully

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to the fore (Liceras et al., 2008, and articles therein). A feature is a unit of grammar that reflects

variation across languages. Features reflect grammatical meanings (such as tense, case,

finiteness) or conceptual meanings (such as evidentiality, habitual aspect, definiteness). These

grammatical and semantic features are captured in Functional Categories (FC), phrase structure

projections that come on top of lexical projections in a tree and provide the grammatical

structure of each clause. There can be many features subsumed in one FC. The FC of Tense, for

example, hosts a variety of features regulating the movement of the verb, the subject case and its

expression, among others. It is of crucial importance to distinguish between features (the

grammatical meanings) and their overt expressions (frequently through inflectional morphology).

For example, Mandarin Chinese has been argued to have null case, regulating comprehension of

Noun−Verb−Noun sentences (Li, 1990). It also does not express past tense with overt

morphology. Those would-be examples of grammatical features with a null expression but

enormous consequences to sentence comprehension. Overtness of functional morphology plays a

role in predictions about learner behavior, such, for example, that L2 overt morphology is easier

to acquire when your native language has a similar affix. Jiang, Novokshanova, Masuda and

Wang (2011) showed that Russian learners of English, unlike Japanese learners, were reliably

sensitive to English plural errors in an online task. The authors attributed this differential

sensitivity to Russian having overt plural morphology while Japanese lacks such morphemes.

Features that contribute to the sentence meaning, such as tense and aspect, are labeled

“interpretable features.” Other features do not contribute to sentential meaning, but rather have

grammatical import only. These features are called “uninterpretable features” and include Case

and grammatical gender. Moreover, the theory nicely accommodates the fact that a single head

of a FC can have any number of features associated with it and be morphologically expressed.

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For instance, languages that encode grammatical aspect often have a single morpheme that

expresses both tense and aspect. This means that the “feature bundle” on the past morphology

instantiates at least two features.

Current GenSLA theories makes use of the above distinction. For example, a modern

version of no or limited accessibility to UG captured under the Interpretability Hypothesis

(Hawkins & Hattori, 2006; Tsimpli & Dimitrakopoulou, 2007; Hawkins & Casillas, 2008)

argues that only the meaningful, or interpretable, features remain accessible to adults in a second

language. Such approaches do not take the position that UG is inaccessible per se in adulthood,

but rather that purely grammatical (uninterpretable) features, not available in the L1 for transfer

present an insurmountable barrier to L2 learners. And so, there is partial access to UG; that is,

there is a critical period effect for uninterpretable features. The claim is that inaccessibility to

uninterpretable features explains much variation attested in adult L2 grammars. The fact that

native Chinese speakers of L2 English—for example, the famous case study of Patty studied

over two decades by Lardiere (1998, 2007)—often omit 3rd person singular agreement

morphology in obligatory contexts in English would be captured straightforwardly because

Chinese does not instantiate the uninterpretable features for subject–verb agreement.

At roughly the start of the millennium, one could appreciate that GenSLA had shifted its

attention well beyond the two classical questions related to UG-accessibility and L1 transfer,

especially as simple binary answers to them were concerned. As can be appreciated above,

theories such as the Interpretability Hypothesis reflect the desire in modern GenSLA to engage

more directly with the dynamic nature of variation in performance as well as in competence. To

be clear, there is no doubt that at some level adult SLA is different from child L1 acquisition in

its process and typical outcomes. Notwithstanding, evidence in support of adult accessibility to

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(at least some properties of) UG (e.g. evidence of true PoS in L2 acquisition) had reached a

critical mass (see White, 2003) by the early 2000s. This motivated GenSLA theorizing to focus

on and explain the documented differences between L1 and L2 linguistic knowledge and

performance outside of the domain of UG-accessibility alone, as well as individual-level

variation across L2 learners. The Missing Surface Inflection Hypothesis (Haznedar & Schwartz,

1997; Prévost & White, 2000); the Feature Reassembly Hypothesis (Lardiere, 2009), the

Prosodic Transfer Hypothesis (Goad & White, 2006), the Competing Systems Hypothesis

(Rothman, 2008), the Bottleneck Hypothesis (Slabakova, 2008) and the Interface Hypothesis

(Sorace & Filiaci, 2006; Sorace, 2000; 2011) are examples of generative-based hypotheses that

have proposed various factors as deterministic for some cases of L1-L2 differences while still

assuming that there is unabridged access to UG in adulthood. These hypotheses offer processing

constraints and limitations, competition between acquired (implicit) and pedagogical (explicit)

mental grammars, reconfiguration of formal features into new L2 bundles, the hypothesized

greater difficulty of morphology as compared to syntax and semantics, as well as L1 prosodic

influences—either independently or in combination—as factors contributing to and/or explaining

specific variation in L2 acquisition. Although space limits a detailed discussion, we will review

a few of these hypotheses in more detail below.

A welcome development within GenSLA stemming back two decades is the proposal that

features and linguistic mental representations may indeed be target-like in L2 mental grammars

even when production or comprehension is variably non-target-like due to additional processing

pressures. One such theoretical account is the Missing Surface Inflection Hypothesis (MSIH)

(Haznedar & Schwartz, 1997; Prévost & White, 2000), which attributes some production

variability to imperfect lexical access to FC exponents. When more specialized forms in a

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paradigm are not lexically accessible, they are substituted by a default form, for example, an

infinitive or a singular noun. Such an approach is falsifiable because it makes predictions that are

amenable to empirical scrutiny. The MSIH, for example, would predict that sufficiently

advanced adult L2 learners who show variable production of inflectional morphology will

demonstrate two things: (a) markedly better comprehension of the same morphology they

variably produce and (b) when producing so-called morphological errors, these should not be

random but rather predictably constrained by markedness factors; that is, to be the default, or

unmarked, morphological exponent.

Another account, the Interface Hypothesis (e.g., Sorace & Filiaci, 2006; Sorace, 2011)

capitalizes on the heightened processing burden of keeping track of grammar and discourse at the

same time. Sorace argues that incorporating contextual information into the sentence meaning

calculation heightens processing costs, and as a result even near-native speakers sometimes

variably apply otherwise native-like mental representations and language processing strategies.

Moverover, Sorace (2011) claims that there might also be a general bilingualism effect at play

here. In other words, even if the processing strategies are shared between an L1 and a target L2,

the mere fact that two grammars are simultaneously active in the mind of the L2 speaker entails

that variable performance might obtain at particular interfaces.

The Feature Reassembly Hypothesis emphasizes that acquisition of the functional

morphology is much more than acquiring binary parametric values. Assembling the particular

lexical items of a second language requires that the learner reconfigure features from the way

these are represented in the first language into new formal configurations (i.e., feature bundles)

on possibly quite different types of lexical items in the L2. (Lardiere, 2009, p. 173). These recent

hypotheses, the Interpretability Hypothesis, MSIH, the Interface Hypothesis, and the Feature

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Reassembly Hypothesis, are just a few examples of how GenSLA theorists use generative

linguistic constructs (grammatical features with and without meaning, linguistic interfaces,

feature bundles) to account for some well-known L1−L2 differences.

Since the turn of the millennium, in parallel with changes in formal generative theory as

well as L2 acquisition evidence itself, contemporary theories within GenSLA as reviewed in this

section have been much more concerned with explaining variation at the group and individual

level. This means that this modern shift in GenSLA brought with it broader recognition that

other variables, historically assigned less importance in the paradigm, needed to be incorporated

more directly. As of the writing of this article in 2016, broader recognition of other variables

had close to two decades of development within GenSLA.

Modern GenSLA Within the Wider SLA Field

Now that we have provided an update of current GenSLA theorizing, we direct our

attention towards contextualizing GenSLA within the wider field of SLA. In doing so, our aim is

twofold. First, we highlight how GenSLA has expanded both the remit of variables and

populations it considers to explain individual variation in SLA, as well as the battery of

methodologies it actively employs, corresponding to more sophisticated behavioral

experimentation and especially psycho/neurolinguistic methods. Second, we explicitly make the

case for why SLA studies benefit from competing theoretical approaches and how GenSLA is far

more compatible with other theories than is commonly believed. Before we can address these

two goals properly, we will acknowledge and discuss points of incompatibility with theories that

deny a domain-specific linguistic capacity. In turn, we highlight what the explanatory benefits

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are from being open to the possibility that the mind is indeed pre-programmed specifically for

the task of language acquisition.

What is different about generative approaches? Poverty of the Stimulus

Before examining and making a case for significant compatibility across various

approaches to SLA, we must be clear that there are non-trivial differences between linguistic

innatist theories and those that reject any type of linguistic domain-specificity. The most

important point of contention is the logical problem of acquisition and by extension the very

existence of UG as domain-specific knowledge. Recall that UG itself embodies an attempted

answer to the logical problem. UG is the purported gap-filler between ultimate attainment

competence and what can be done via available input/intake and domain-general cognition. If

there is no disparity in resulting linguistic competence between available input and what domain

general learning should be able to construct, then there is indeed no need for UG. The main non-

trivial point of difference then is whether or not there truly is a logical problem of acquisition.

To be concrete, let’s discuss one example of a PoS learning situation provided by

Martohardjono (1993), a study documenting knowledge of Subjacency violations and wh-

movement. The Subjacency Condition was probably the most studied principle of UG in the 80s

and 90s (Johnson & Newport, 1991; Schachter, 1990; see Belikova & White, 2009 for a review).

Subjacency regulates the behavior of wh-words and phrases. In languages like English wh-

phrases move to the left periphery of the sentence, although their movement is highly

constrained (Ross 1967); in other languages, such as Chinese and Indonesian, wh-phrases remain

in situ close to the verb. Martohardjono tested native speaker of Indonesian, Italian and Chinese,

languages in which Subjacency applies differently as compared to English. She tested rejection

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rates of ungrammatical constructions of two types: wh-islands and extractions out of relative

clauses. These sentences look superficially similar and the obvious analogy suggests they should

be treated in a similar manner. However, linguistic theory has identified that these two

extractions differ in acceptability.

(1) ??Which boy did Amy wonder [CP why had _____ brought the parcel]]?

(2) *Which phonebook did Sue call the doctor [CP that _____ listed]]?

Sentences as in (1) violate Subjacency, but do not lead to strong ungrammaticality: these

are called weak violations, which is signaled by the two question marks. They should contrast in

the reader’s judgments with strongly unacceptable sentences as in (2), which violate Subjacency

and another linguistic principle, the Empty Category Principle, which requires certain empty

categories, namely, traces of movement, to be properly governed. Sentences as in (2) are

considered to be strong violations and are marked as ungrammatical with a star. The concrete

linguistic analyses are irrelevant to the point we want to make: the differences in acceptability.

Table 1

Rejection rates (percentages) of strong and weak violations, (based on Martohardjono, 1993,

Table 18 on p. 124)

Native language Weak violations

as in (1)

Strong violations

as in (2)

English 79 94

Italian 61 89

Indonesian 42 87

Chinese 38 76

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The distinction between the acceptability of the two types of sentences as in (1) and (2) is

clearly present in the judgments of the native English speakers, as can be seen in Table 1. Why

does this difference in acceptability constitute a PoS situation? Neither type of sentence appears

in the input addressed to learners, since they are unacceptable. If acceptability is a matter of how

many constituents come between the gap and the moved phrase (the so-called extraction

complexity effects, Gibson, 1998, among many others), in the unacceptable sentence (2) the

moved phrase jumps over fewer constituents compared to the more acceptable sentence in (1), so

the former should be somewhat easier to compute. It is remarkable that the same pattern of

acceptability demonstrated by the native controls is exhibited by the learners as well. Even more

remarkably, the nativelike pattern differentiates between two relatively complex and

unacceptable types of sentence, which the learners cannot transfer from the native language and

they have not been taught to reject. Such findings and others like it (e.g. Dekydtspotter, Sprouse

& Anderson, 1998; Dekydtspotter, Sprouse & Swanson, 2001; Hopp, 2005; Lakshmanan et. al.,

2009; Marsden, 2009; Montrul & Slabakova, 2003; see Schwartz & Sprouse, 2013 for a range of

PoS situations) are suggestive of access to universal grammatical principles.

In principle, it should be relatively easy to disprove claims of a logical problem: show

that there are in fact no instances of PoS or, when it is agreed by all that input alone is

insufficient to explain resulting competence, that the grammatical knowledge in question falls

out straightforwardly from domain general cognition and/or processing principles. That there is

in fact no logical problem has been argued rather extensively (e.g. Evans, 2014; Tomasello,

2003; Bybee; 2010; O’Grady, 2005; Goldberg, 2013; Gries, 2012; Redington, Charter & Finch,

1998; Gerken, Wilson & Lewis, 2005). No cognitive-based theory denies the reality of low or

even zero input frequencies, that is, properties and constructions that appear rarely or not at all in

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the input. And so, the main difference revolves around what is proposed to fill the apparent gap

between attested knowledge and lack of specific evidence for that knowledge. Within generative

theories, these are properties whose successful acquisition is attributed to UG. From the

viewpoint of other cognitive theories, such grammatical properties simply fall out from statistical

learning, domain general cognition and/or processing considerations. In principle, both

explanations are possible. However, our point is that the path of how learning actually

happens―exactly how domain general cognition and/or processing principles fill the gap

between the input and the specificity of the ensuing competence―must be articulated and

demonstrated for each of the low and zero frequency structures before UG is completely

abandoned.

Generative theory has been describing and explaining PoS for five decades (Schwartz &

Sprouse, 2000, 2013). Each theoretical proposal for a PoS property provides not only the

description of the learning task, but also a proposal of how it is overcome. At present, property

theory in usage-based paradigms has not yet attempted this exhaustively. It is not enough to

show that some (perhaps many) discrete domains of grammar can be acquired on the basis of

available input and/or domain general cognition/processing; it must be shown that every one of

the documented cases can be accounted for in the same manner (cf. Schwartz & Sprouse, 2013;

Valian, 2014). No matter how reduced the set of properties turns out to be for which a domain-

specific language mechanism is required, linguistic innatism prevails to the extent that there are

any properties that cannot otherwise be fully accounted for. To be fair, there have been recent

attempts to provide alternative explanations regarding specific properties of UG from an

emergentist perspective, for example, interpretation of pronouns and reflexives (O’Grady, 2005,

2008) formally captured under Chomsky’s principles of the binding theory (Chomsky, 1981).

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Still, there remain far too many properties of grammar for which there are no (or not yet)

parsimonious alternative accounts that explain the resulting grammar from an interaction of input

and domain general cognition/processing. In sum, to remove PoS from the equation, this venture

needs to be exhaustive and time will tell how successful O’Grady and colleagues will be.

The centrality of linguistic theory

An important advantage of acquisition paradigms that adopt an innatist perspective on

language (and in this we include all theories that adopt a formal linguistic approach, be it

Minimalism, [generative] Lexical Functional Grammar, Head-Driven Phrase Structure Grammar,

Optimality Theory, among others) is the level of prediction―and by extension explanatory

power―they have as a result of the granularity of the adopted theories. Formal linguistic

theoretical granularity affords two important things for acquisition research as it relates to

descriptive and explanatory powers. Firstly, proposals from formal theory provide a roadmap of

what to look at/for, inclusive of what array of properties might be good to examine together.

Linguistic properties that have little obvious surface connection, yet are argued by theoretical

proposal to be inherently related to each other at an abstract level (e.g., properties at linguistic

interfaces, properties related to the same functional category), give the researcher a starting point

on what is interesting to test as well as a model by which superficially unrelated properties can

be understood. In other words, formal theory provides principled predictions a priori. An

example is provided by the syntax-before-morphology discussion in White (2003:187–193): only

looking at all the properties that are associated with the functional category of Tense can we

ascertain that most learners know the syntactic properties before they supply the functional

morphology exponent of Tense to criterion.

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Secondly, formal linguistic theory (as a foundation of acquisition proposals) provides a

way to make sense of bodies of data, not only discretely on a property-by-property level but also

how data sets fit together to elucidate developmental stages and explain the complexity of a

given linguistic system. Linguistically savvy explanations look at development as the growth of a

grammatical system, as argued by Hawkins (2001) for the morpheme studies from the 1960s (see

also Zobl & Liceras, 1994).

Two consequences of relying on linguistic theory emerge: (1) acquisition data of all types

can be used to falsify theoretical proposals themselves and (2) one avoids the circular

argumentation that there is a one-to-one relationship between late acquisition, variability and

computational complexity. For many reasons (e.g., the cost of bilingual processing, labored

lexical access, slower reading and reactions), it does not have to be the case that complexity and

ease/timing of acquisition map onto each other completely. New hypotheses in GenSLA theory

are in a position to seamlessly explain the different contributions of computational complexity

and these other factors that give rise to difficulty and variability.

An example of such an approach is provided by the Interface Hypothesis (Sorace &

Filiaci, 2006; Sorace, 2011) that we introduced above. Much work in the early 2000s up until the

present day has focused on modeling interfaces, points in linguistic computation where

information across modules (e.g., syntax and semantics, syntax and discourse) is integrated. The

proposal is that properties at interfaces are more computationally complex precisely because they

require information integration across domains. A further insight comes from the proposal that

not all interfaces are the same. Rather, interfaces between linguistics domains (e.g. syntax and

semantics) are less taxing on the limited processing resources of the brain than when information

must be integrated between a linguistic component and a, strictly speaking, non-linguistic one

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(e.g., syntax and discourse). The Interface Hypothesis capitalizes on these theoretical insights in

arguing that external interfaces such as the syntax-discourse interface will prove more

problematic for L2 adults than internal ones such as the syntax-semantics interface (cf. Tsimpli

& Sorace, 2006). Although it has spawned a great deal of research in recent years, evidence to-

date is unclear as to whether the hypothesis is accurate or generalizable (see Montrul, 2011;

Lardiere, 2011; White, 2011, for discussion).

Using formal linguistic theory opens another avenue that relates to L1 transfer. Recall

that generative theory provides robust descriptions as well as formal proposals on how specific

properties work and are mentally realized. As a result, it is possible to model, under comparable

conditions, which L1–L2 language pairings will have more or less problems with SLA in a

property-by-property manner. Of course, the same can be done simply to render predictions

about a single pairing. For example, where can linguistic theory predict stumbling blocks along

the interlanguage continuum for an English L1 speaker learning L2 German? How will this

differ if the L2 is Farsi, Italian or Swedish? The notion of formal features and their bundling on

lexical items, as discussed above, again proves crucial. As stated before, the concept of feature

bundles allows for a more nuanced way of looking at linguistic properties, especially variation.

So, while it might be the case that languages superficially have analogous forms that

significantly overlap in meaning, the task of an L2 learner is to reconfigure the bundle of features

of specific lexical items to match those of the target grammar. Formal linguistic descriptions tell

us what the precise compilation of these feature bundles is. To the extent that L1 and L2 feature

bundles overlap, no remapping is needed. To the extent they differ, the difference itself defines

the L2 learning task, whereby some transferred features from the L1 may need to be removed

from the corresponding L2 bundle, whereas others may need to be added via L1 remapping or

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simply newly acquired if the L1 lacks a feature altogether. This inherent complexity of feature

bundles and the possibly different conditioning environments for specific features in a bundle

entail that not all features of a particular FC may be learned at the same time.

Although there is no question that frequency in the input matters a great deal (see the next

subsection), it is equally clear that there are limits on the explanatory power of input frequency

in L2 acquisition (cf. VanPatten & Williams 2007; 2014). A second line of research addressing

linguistic variability and difficulty shows this nicely. Let’s take for example, obligatory

morphology in the target language. When morphology is obligatory, like third person singular -s

marking in present tense or -ed past marking in English, it is provided reliably, at least in native

input, 100% of the time for relevant contexts and is often quite frequent irrespective of how

frequency is measured.1 Moreover, for the vast majority of L2 learners who are formally trained

in the target L2, explicit teaching of morphology is abundant, repetitive over time and supported

with correction and feedback. Notwithstanding, research and anecdotal observation both show

that morphological suppliance in L2 production is highly variable, even in learners who are

otherwise demonstrably highly proficient and even when the L1 also has similar obligatory

morphology in the same domain. Recent GenSLA studies have focused on why this might be.

For example, Lardiere’s (2009) Feature Reassembly Hypothesis, Slabakova’s (2008) Bottleneck

1 We thank Stefanie Wulff for running the COCA analysis for us to get the numbers presented just below. The

Corpus of Contemporary American English (COCA, http://corpus.byu.edu/coca/), a 520-million-word corpus:

The POS-tag for any verb in any inflection (tag: _v*) occurs 53,917,380 times.

The POS-tag for third person singular -s on lexical verbs (tag: _v?z*) occurs 20,677,034 times (38.3% of all verbs,

and 3.9% of all words).

The POS-tag for past tense -ed on lexical verbs (tag: _v?d*) occurs 15,108,279 times (28% of all verbs, and 2.9%

of all words).

As another indirect measure, we refer the reader to Wulff et al. (2009). Although they did not give tag frequencies

directly, they focused on the normalized frequencies the 100 most frequently occurring verbs in any tense-aspect

configuration to build an argument for learnability based on Zipfian distributions. These frequencies clearly

demonstrate that the forms occur substantially often.

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Hypothesis, Goad and White’s (2006) Prosodic Transfer Hypothesis, among others, offer

empirically falsifiable predictions that attempt to explain why, despite frequency, morphology

proves so problematic in L2 use.

Understanding acquisition in this way—an updated version of parameter resetting—

enables us to capture the subtleties of the L2 learning task for specific language pairings

(L1→L2) even and especially when two languages in a pairing have a similar property, broadly

speaking. In this way, formal linguistic descriptions themselves reveal experimental predictions

for acquisition and performance. Because linguistic descriptions generally capture the facts of

specific languages well—disagreements are usually limited to particular explanations not the

descriptions themselves—and in recent years they come in the form of feature configurations,

one can straightforwardly use them to derive predictions between typologically similar and

distinct language pairings. Descriptions of feature bundling not only capture subtle differences

well; they provide an easy way to model learnability predictively over time.

Similarities between GenSLA and other cognitive theories: Input matters and matters of input

Having reviewed macro-level theory differences, we now turn to commonalities between

generative and other cognitive approaches, specifically as they relate to the importance of the

input learners are exposed to.

Within GenSLA, the importance of the input has always been assumed, but until the last

decade and a half it was not highlighted or emphasized as much as it should have been (for an

exception, see Carroll, 2001). A newer idea in generative theorizing is that L2 convergence

crucially depends on how much evidence in the input there is and how clear such cues are in the

input itself (e.g., Rankin & Unsworth, 2016; Slabakova, 2013; Westergaard, 2009; Yang, 2002;

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Yang & Montrul, 2017). In the sense that input is indispensable for acquisition, GenSLA is, to a

point, compatible with statistical learning approaches to acquisition. For example, learning

lexical items and set expressions clearly happens through some mechanism of frequency and

collocation-based statistical learning. By the GenSLA account, access to input is the main

driving force of parameter resetting (White, 1989, 2003). The context under which input is

provided is of crucial importance as well, especially in SLA, since context itself is a partial proxy

for quantity and quality of input as well as a delimiter of potential language use. On these points,

we all agree. However, generative approaches maintain that input factors have more limited

effects than other paradigms claim.

Of course, no theory of SLA maintains that input alone is the sole driving force. For both

GenSLA and usage-based approaches, the fact that learners already have a fully developed

language at the outset of L2 learning is significant because it affects the way input becomes used

in the acquisition process (e.g., converting input into intake). In recent years, many generative

acquisition studies have examined the role of the input in explaining patterns of

development/acquisition, highlighting both the crucial role input plays and, somewhat differently

from usage-based approaches, the limits input has on some areas of linguistic development.

Studies examining potential differences by context of L2 acquisition, for example between

classroom L2 learners and naturalistic L2 learners, where quantity and qualities of input vary in

obvious ways, show promising results. In the typical case, naturalistic exposure, especially study

abroad, would furnish richer and more varied language experience. In a telling example study,

Pliatsikas & Marinis (2013) examined the processing of two similar groups of Greek-English

bilinguals with the same age of acquisition (8-9 years). Using long-distance wh-movement

stimuli, they found that their naturalistic learners (but not the classroom learners) were indeed

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processing the intermediate copies of movement just like native speakers. These results are in

line with the importance of ecologically valid experience for nativelike and efficient parsing, as

well as acquisition.

In the previous section, we highlighted that the abundant frequency of tense and

agreement functional morphology (e.g., –s, –ed) does not translate into superior suppliance in L2

production (VanPatten, Keating & Leeser, 2012). Recently, generative studies have also focused

on qualitative factors related to the role that variation in the input has on ultimate attainment

across grammatical domains, even within core syntax. Meisel et al. (2011), Miller (2013), Miller

& Schmidt (2012), Montrul & Sánchez Walker (2013), Rothman (2007), Unsworth (2014), Yang

(2002), as examples, show how issues pertaining to quality (including ambiguities), quantity and

inconsistencies in the input affect both the rate at which properties are acquired and have

lingering effects in ultimate attainment. Moreover, such studies demonstrate how input factors,

as well as other sociolinguistic variables such as socioeconomic status, can be modeled within a

generative framework (Yang, 2002; Yang & Montrul, 2017). Directly examining the role of

qualitative input factors has been more significant to date within generative approaches to

monolingual or bilingual child language and adult ultimate attainment outcomes. Incorporating

the same guiding questions in examining learners in a range of proficiencies will be of increasing

importance in the near future.

Psycholinguistics brings new research techniques and methods

One criticism of GenSLA we often hear relates to its experimental limits; that is, the

perception that grammaticality judgments tasks (GJT) are either overused or even exclusively

used. The main issue seems to be that GJTs are not true reflections of how language is actually

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used. To start, it is simply not true that GenSLA studies limit themselves to the GJT

methodology. GJTs rarely stand alone, that is, they are simply part of a suite of tasks testing the

same properties in varied ways. In addition to GJTs, GenSLA studies have employed other

behavioral tasks such as picture verification tasks, scalar judgment tasks, context felicity tasks,

constrained/forced elicitation tasks, repetition tasks, open-ended elicitation tasks, closed/fill-in

the blank production tasks, to name just a few. Whole strands of GenSLA research, for example

studies on semantic interpretation, use predominantly Truth Value Judgment Tasks, among a

variety of other interpretation tasks (e.g., Dekydtspotter, Sprouse & Swanson, 2001).

Considering GenSLA over at least the past 15 years, one would be hard pressed to find published

work that exclusively used GJTs.

Nevertheless, GJTs are indeed a staple within GenSLA precisely because of GenSLA’s

interest in trying to tap underlying representation as opposed to being uniquely concerned with

variation at the level of production. To be sure, knowing what is actually produced by L2

learners is of great importance, hence the production measures we often include as part of our

testing batteries. However, GenSLA is equally interested in determining what L2 learners’

intuitions are with reference to ungrammaticality, semantic and contextual unacceptability. GJTs

and truth judgment tasks are indeed a good way to determine not only what L2 learners know is

acceptable, but crucially if they also know that certain structures are not acceptable in the L2,

especially for properties that would be acceptable in their L1. Since GJTs isolate grammatical

intuitions, they are a good means to determine the composition of L2 feature bundles (e.g., tease

apart number from gender knowledge).

The relationship between psycholinguistics and generative grammar is a long one. In

fact, it would not be a far stretch to say that the original idea of UG stems from the idea that there

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is a rich relationship between processing and grammatical representation. The alignment between

psycholinguistics and GenSLA itself is also not new, but it is fair to say that the upsurge in

interest focusing specifically on L2 processing is fairly recent. Nowadays, GenSLA has not only

aligned itself better with psycholinguistic inquiry, characterized by shifts in methodological

design and experimentation techniques, GenSLA is also using processing findings to

address/make claims regarding debates on L2 competence. Take for example, the Shallow

Structures Hypothesis (SSH) (Clahsen & Felser, 2006), which argues that L2 processing is

qualitatively different from L1 processing because only the latter employs complete underlying

representations. The SSH is considered a mainstream theory of L2 psycholinguistics, in fact

potentially the main promoter of the surging interest in L2 processing since the early 2000s (cf.

Keating & Jegerski, 2015). Because it most directly corresponds to claims of processing proper,

its main thesis can be applied within multiple theories of linguistic representation. However, the

SSH is predicated, at least in the minds of its authors, on a UG understanding of linguistic

representation and mental computation. Returning again to Sorace’s (2011) Interface

Hypothesis, we see yet another example of an important mainstream psycholinguistic proposal

that is grounded in a generative understanding of language.

With the enhanced interest in psycholinguistics in recent decades, methodologies

employed by GenSLA scholars have expanded as well. Eye-tracking is now used abundantly by

GenSLA scholars (e.g., Clahsen, Balkhair, Schutter, & Cunnings 2013; Cunnings, Batterham,

Felser & Clahsen, 2010; Felser & Cunnings, 2012; Hopp & León Arriaga, 2016; Hopp, 2013;

Kim, Montrul & Yoon, 2015). The EEG/ERP method is also being used by GenSLA scholars in

recent years, specifically to test neurological correlates of GenSLA hypotheses (e.g., Alemán

Bañón, Fiorentino, & Gabriele, 2014; Alemán Bañón, Miller & Rothman, 2017; Gabriele,

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Fiorentino, & Alemán Bañón, 2013; Rothman, Alemán Bañón & González Alonso, 2015;

Reichle & Birdsong, 2014; Sabourin & Stowe, 2008). For example, Alemán Bañón, Fiorentino,

and Gabriele (2014) examined the processing of grammatical gender and number in English L1

learners of L2 Spanish, arguing that ERPs could be used to test the Interpretability Hypothesis

(Tsimpli & Dimitrakopoulou, 2007). As described earlier, the Interpretability Hypothesis claims

that uninterpretable features—those that are purely grammatical in nature, or core syntactic

features—not instantiated in the L1 will not be acquirable in a native-like manner by L2 learners.

Alemán Bañón et al. proposed that if the Interpretability Hypothesis is correct, then one should

expect L2 learners to show qualitatively different processing for the purportedly unacquirable L2

features. Since English has grammatical number but not grammatical gender, the predictions of

the Interpretability Hypothesis would be that the L2 learners might show evidence of nativelike

processing for number violations, but not for grammatical gender violations. In the event, the

study showed that by advanced stages of L2 acquisition, English learners of Spanish do have

qualitatively similar processing for both gender and number violations. Specific results are,

however, of less consequence to our point, which was to provide an example of how

psycholinguistic and neurolinguistic methodologies are being used in GenSLA and in ways that

add to theory-internal debates as well as contribute to psycholinguistics more generally.

Another long-standing idea is being reinforced with evidence from psycholinguistic

findings recently: that perceptions of L1–L2 acquisition differences may in part be due to

processing effects; that is, while learners grammatical representations are indeed in place, their

slower and labored processing produces an impression of a faulty grammar (as in the case of the

MSIH). One example comes from Hopp (2013, 2015), who has argued that differences in the

input between natives and L2 learners can lead to unstable lexical representations of L2 gender

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and problems with gender assignment lexically, hence slower lexical access provides the

semblance of errors even if competence is grammatically constrained. In turn, lexical effects may

produce non-target processing of the syntactic aspects of gender agreement, such as predicting

what is to come next in the sentence. Thus, the long-standing debate on whether L2 learners are

fundamentally different from native speakers is seen in a new light: while L2 competence may

be fundamentally similar, L2 processing might not be, or might not be as efficient (see also

Grüter, et al. 2015; Kaan, 2014).

Furthermore, the conventional division of labor between underlying linguistic

representations and the parser2 has been reconsidered in the parsing-to-learn proposal (Fodor,

1998) that the parser is in a symbiotic relationship with the language acquisition device (cf.

Dekydtspotter & Renaud, 2014; Phillips & Ehrenhofer, 2015). In essence, the idea is that

learning happens through processing failure (e.g., VanPatten & Cadierno, 1993; Carroll, 2001).

The incremental structural analysis of the input and the subsequent re-analysis, when the input

cannot be parsed by the interlanguage grammar, provide the triggers for grammar acquisition.

This is a potent transition theory that has a high potential to explain how learners move from one

stage of knowledge to another.

New populations added to the inquiry

In the last decade or so, there has been a sharp increase in generative studies examining

populations complementary to typical adult L2 acquisition, for example, heritage bilingualism,

child L2 acquisition and third or additional language (L3/Ln) acquisition. Together with adult

2 Linguistic processing is executed by the parser, which is a language-neutral grammatical analyzer. Parsing

involves the rapid and automatic assignment of grammatical structure to a sentence encountered in speech (e.g.,

Pritchett, 1992:1), without which form and meaning cannot be mapped one onto the other.

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learners, these new populations help to paint a comprehensive picture of the human language

faculty in action. Comparisons between these populations and adult L2 acquirers also provide

new evidence for perennial debates within SLA studies, for example, the Critical Period

Hypothesis (CPH).

As is now well known, heritage language bilingual grammars typically diverge in their

ultimate attainment from age-matched monolingual norms (Montrul, 2008, 2016). This is true

despite the fact that heritage bilinguals are native speakers of the heritage language and the

acquisition process takes place naturalistically in early childhood (Rothman & Treffers-Daller,

2014). Differences between monolinguals and heritage speaker adults and monolinguals and

adult L2 learners partially overlap (e.g., Montrul, 2012). The mere fact that bilingual naturalistic

childhood acquisition (in heritage speakers) can result in significantly different grammars by

adulthood, reminiscent of the types of divergences observable in adult L2 grammars, sheds doubt

on the CP claim that age is the main deterministic variable. Heritage speaker bilingual data

reveal that prepubescent acquisition does not guarantee convergent acquisition. And why would

it? After all, despite being child native speakers, they have grown up in bilingual environments

where access to the heritage language is highly limited in quantity, the quality of the input is

likely different from what monolinguals receive, access to literacy and formal training may be

sporadic, and so on. These same facts apply to adult L2 acquisition as well. And so, if such

comparative differences to monolinguals obtain even for naturalistic child bilinguals where

explanation cannot be reduced to CP effects precisely because heritage speakers were child

acquirers, there is no reason to view similar outcomes in adult acquirers as evidence of a CP in

SLA.

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Another population becomes crucial when questions of fundamental similarity or

difference are invoked: child L2 acquirers. If a child is exposed to the nonnative language

between the ages of 4 and 7, she is classified as a child L2-er. Schwartz (1992, 2003, 2009, see

also Lakshmanan 1995; Haznedar, 2013) calls the child-adult L2 comparison the “perfect natural

experiment” (2004:17). The logic of the CPH entails that adult and child acquirers should

demonstrate fundamentally different pathways of development. For example, in Johnson and

Newport’s classic (1989) study, the child acquirers were generally more successful than those

who started as adults, and a negative age-to-nativeness correlation was observed. Thus, if

research uncovers evidence that the developmental paths of child L2 and adult L2 look similar,

in the sense that they make the same types of errors and exhibit the same developmental stages,

this would question the claim that differences in developmental sequencing path between child

L1 and adult L2 can be attributed to inaccessibility to UG. The reason is because under any

generative approach, child L2ers under the age of 7–8 have access to UG. And so, if child L2ers

and adult L2ers of the same L1 have the same developmental trajectory, it is likely that the basis

of difference is the shared experience they have with their L1. If, on the other hand, children and

adults acquire along different developmental continua, this would support claims that adult L2

acquisition is not UG-constrained but is instead due to explicit learning, various problem-solving

strategies and superficial noticing of linguistic rules. Understanding child L2 acquisition more

completely over the next decade or so will have the knock-on effect of fine-tuning adult SLA

theories.

Generative acquisition scholars have also shifted focus towards multilingual acquisition,

that is, the acquisition of a third or additional language. One small offshoot of the larger

research program is especially interesting for debates in L2 acquisition, again for the claims

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related to the CP. Iverson (2009, 2010) proposed that testing the very initial stages of L3

acquisition could shed a unique light on claims related to the so-called critical period for syntax.

The logic is as follows: if adult L2 learners are able to transfer properties at the very beginning of

L3 acquisition that are only available from an L2 grammar because such properties are not

contained in the L1, then multilingual transfer itself can be used as evidence against a strict

interpretation of the CP for SLA. To demonstrate this properly, he proposed that such transfer

cannot be superficial, that is, one must examine properties that could not be reasonably learned

via explicit rules, but rather reflect acquisition in the truest sense. The best candidates for

relevant L3 properties to be tested are those that are L2 PoS properties, since these should only

come as a by-product of true L2 acquisition. Rothman and Cabrelli Amaro (2010) follow this

logic, adding to the overall methodology a comparison of ab initio L2 and L3 learners who share

the same L1. Combined, these studies show that the beginning stages of L3 interlanguage can be

characterized by properties that must have come from proper L2 acquisition at the level of

underlying representation. If on the right track, then these data sets also cast doubts on the CPH

in SLA.

Conclusion: A Place for Multiple Theories in SLA

Having traced the trajectory of GenSLA over four decades, we now shift to specifically

carving out its place in the broader study of SLA theory. In recent years, it has been argued that

SLA studies as a macrofield benefits from a multiplicity of approaches, precisely because a

single approach, at least at present, is not equipped to adequately address all the dimensions

pertinent to SLA (cf. Rothman & VanPatten, 2013; Slabakova et al. 2014, 2015; VanPatten &

Rothman, 2014). To name a few, there are social, individual and cognitive aspects to SLA. And

33

while no one denies that these aspects interact in nontrivial ways, it is not necessarily the case

that paradigm-internal priorities and/or methodological expertise allow for equal treatment of all

aspects. This fact might reflect more the relative youth of SLA studies than anything else;

however, it should be fairly uncontroversial to claim that at present theories with a primary focus

on the social side of acquisition will not be able to engage as fully with the cognitive aspects of

acquisition to the same extent that cognitive theories do and vice versa. The questions posed by

each, all worthy of serious inquiry, are simply different. None are better or worse and none

should be privileged as all contribute to the puzzle that is SLA. The primary imperative of each

paradigm is to test theory-internal proposals of a select domain of SLA, discard proposals

through scientific inquiry along the journey and arrive at a place of relative agreement. When

theory-internal proposals have been exhaustively tested and paradigm-specific consensuses are

more solid, transitional theories of SLA that incorporate all aspects might be possible. The field

as a whole is simply not there yet.

As we hope is clear at this point, because GenSLA (as well as all other cognitive

approaches) focuses on only some aspects of the entirety of the SLA process, it is not

incompatible with other foci studied by other traditions. For example, GenSLA says nothing

about social dimensions of language. However, we know that the sociology of language is a

variable that interacts with mental representation. Minimally, language ideologies,

sociolinguistic variation, language policies and linguistic identities affect access to and quality of

language input, the external ingredients needed for grammatical growth. Whatever the case,

there is little proposed by sociolinguistics and generative grammar that is a priori mutually

exclusive. Having a genetic component to linguistic computation and an understanding that

language is a byproduct of human interaction are not at odds. The question does not have to be

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nature vs. nurture, why can it not be both? And so, SLA approaches that focus on motivational

aspects, for example, need not run in contrast to any tenet of generative linguistics. In fact, we

would argue they are completely complementary.

GenSLA is part of the cognitive side of SLA, and so if there are tangible incompatibilities

between theories of SLA then they should be found across competing cognitive theories. Here

too, we suggest that there is much less mutual exclusivity than most—on any “side”—might

agree. As it pertains to acquisition of the lexicon and even acquisition of syntactic properties that

clearly have correspondent cues in the input, the data are neutral to the tenets that seemingly

divide us, that is, the logical question of acquisition. To give a tangible example, there is great

work examining the acquisition of verbal argument structure that could be labeled as strictly

generative (e.g., Juffs, 1996) and strictly usage-based (e.g., Ellis, Romer & O’Donnell, 2016).

Of course, the methodological approaches differ across studies due mostly to paradigm tradition.

While generative scholars investigate acceptability and interpretation through eliciting

judgments, usage-based scholars predominantly look at corpora and linguistic production. This is

so because GenSLA scholars are primarily concerned with learners’ mental representations,

while usage-based scholars are more concerned with what learners do with language, which in

turn is taken to reflect what they know. The interpretations of findings are also shaped by the

working assumptions, terminology and specific questions of the respective paradigm. However,

a neutral reading of the conclusions shows they are not so different. The bottom line in each case

is that L2 learners can acquire novel argument structure and the usage-based approaches even

show how this reflects nicely the probabilistic contingencies of the input in language

use/exposure.

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Perhaps it is not so surprising that the data offered and the ultimate conclusions on

argument structure acquisition do not differ wildly. Argument structure, and the mental lexicon

more generally, is not an ideal domain to examine where these sets of theories actually diverge

with respect to the necessity for innate knowledge. At the same time, there is also a considerable

proportion of acquisition facts that cannot be explained with Zipfian learning,3 salience of the

form and prototypicality of the meaning, all input factors affecting ease and difficulty of

acquisition suggested by Ellis and Collins (2009). To wit, the majority of L1–L2 syntax-

semantics mismatches (discussed in Slabakova 2008, 2016) and feature reassembly learning

situations (Lardiere, 2009) would not find a ready explanation under usage-based procedures.

The semantic differences between the aspectual tenses in English and Spanish constitute one

well-known example of a syntax-semantics mismatch. What Ellis and Collins call “contingency

of form–meaning mapping,” perhaps the most relevant factor for explaining syntax-semantics

mismatches and feature reassembly, does not come close to doing them justice. One cannot make

fine-gained predictions about behavior based on this factor since it is not founded on a

substantially granular property theory.

Our point is that much, maybe most, of what we study under cognitive approaches cannot

address the innateness question profitably. Usage-based approaches nicely explain acquisition

where lexical learning is involved, including functional morphology learning. Generative

approaches do better, in our view, at explaining the acquisition of subtle complexities of

language that do not find direct cues in the input or even indirect cues that should lead to

inductive learning. Moreover, generative approaches are better at connecting properties that are

3 In natural language, Zipf’s law (Zipf, 1935) describes how the highest frequency words account for the most

linguistic tokens. A Zipfian distribution in learning is one where a prototypical, salient and low-variance exemplar is

introduced and learned first, while a full breadth of exemplars is acquired later.

36

superficially unrelated but underlyingly linked to the same parameter, e.g. properties that emerge

at the same time in development (Snyder, 2001), precisely because the granularity of the formal

theory employed can account for this and, in fact, even predicts this. There remain plenty of

properties that allow a head-to-head framework comparison, see specifically Shantz (2017) and

Zyzik (2017) for some good examples. Where we differ incommensurably is in delineating the

parts of language that are claimed to be truly universal and otherwise unacquirable, that is, PoS

properties illustrating the logical problem of acquisition. Some claim that PoS properties simply

do not exist (e.g., Evans, 2014; Pullum & Scholz, 2002). We take that criticism seriously. But

as we pointed out, more than claiming PoS does not exist is needed. What one needs to show, to

eradicate once and for all the very notion of PoS, is to provide alternative explanations for how

properties described in the literature as PoS are acquirable. The descriptions of PoS structures are

not in question, what is in question is that the input itself in consort with domain general

cognition is not sufficient to acquire these properties (O’Grady, 2008).

Our point is simple: many people working on acquisition from either a generative

tradition or a usage-based position currently do not appreciate that the area of mutual exclusivity

is as small as we have claimed here. The good news is that the strict divide between the so-called

sides of cognitive approaches to SLA is more a matter of tradition and mutual misunderstanding

than tangible. Much work can be done at the cross-roads of where data are neutral. No one

needs, therefore, to compromise core beliefs to begin to engage in interdisciplinary research

where our views are indeed not mutually exclusive. Combining efforts means that the results of

such research should be more easily understandable and satisfactory to all sides, no matter what

the results seem to favor in the end. GenSLA scholars, in our view, have much to offer other

SLA subfields as we hope is evident by now, and other subfields of SLA have much to offer

37

GenSLA in terms of methodology and beyond. For example, usage-based theorists have teamed

up with great success in recent years with corpus linguists who hold the keys to a methodology

crucial to revealing facts about language (see e.g., Wulff, in press). We see no reason why the

same could not be true of GenSLA with other traditions of linguistics. Of course, until we have

crystal clear evidence that is truly irrefutable, we will continue to agree to disagree on nontrivial

points. But disagreement should not be a bottleneck to progress for the broader SLA field. It is

our hope, that this invitation is the beginning of many collaborations that help move the broader

field of SLA forward, while respecting the centrality of linguistic theory and the contributions

that each subfield makes in its own right.

Acknowledgements

We are very grateful to the journal editors for inviting us to contribute this state-of-the-science

article. We are extremely grateful to four expert reviewers and to the managing editor, whose

comments made the article considerably clearer and better argued. Work on this article has been

supported by an Arts and Humanities Research Council Research Networking Grant

(AH/M002020/1) awarded to Marsden and Slabakova. This support is gratefully acknowledged.

Over the years, we have discussed in depth many of the issues covered in the present paper

and/or have been influenced by seemingly passing exchanges with many of our colleagues that

we wish to acknowledge with gratitude here, but especially Joyce Bruhn de Garavito, Robert

DeKeyser, Nick Ellis, Tania Leal, Judith Liskin Gasparro, Heather Marsden, Silvina Montrul,

Lydia White, Steffi Wulff, Bill VanPatten, and our many graduate students over the years.

Whether we have agreed or agreed to disagree, your generosity in discussing views, especially

38

when different from ours, has helped shape our current views. The authors’ names appear in

alphabetical order.

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